A Study on the Application of Flash Flood Guidance with Predicting the Risk Level of Guerrilla Heavy Rainfall

Abstract

To alert flash flood warnings on the watersheds of the Toga River basin in Japan, flash flood guidance (FFG) was considered to determine the criteria for whether flash floods occur. FFG is the amount of precipitation needed in a specific period of time to initiate flooding on the watershed. FFG was estimated based on Threshold Runoff (TR) and Soil moisture Deficit (SD) using the Storm Water Management Model (SWMM). In this research, using topographic (i.e., DEM, land use, crosssection, etc.) and meteorological (i.e., radar rainfall intensity) data, FFG was estimated on the mixed land use consisting of the rural and urban areas. So, FFG can issue flash flood warnings without running the entire hydro-meteorological process in the region where flash floods frequently occur. As a result of the calculation of the flash flood guidance, the value at 10 minutes rainfall duration ranges from 9.97 to 23.89 mm when flash floods occur in the Toga River basin.